Chlorine in the form of chlorine gas or sodium hypochlorite has been used for a long time and in great amounts to remove algae from water and also for the oxidative decomposition of oxidizable impurities contained in water. This chlorination, however, has a number of disadvantages in the purification of water and water systems, such as a pungent odor and the tendency to irritate the mucous membranes. Furthermore, it was found that the chlorination of water may lead to the formation of halide compositions which must be regarded as being carcinogenic. The same is true if bromine is used instead of chlorine.
For this reason many attempts were made to use halide-free disinfectants instead of the halide compositions in the treatment of water, especially water in swimming pools. The use of peroxide compositions, for example hydrogen peroxide, sodium or potassium persulfate for degerming water has been known for a long time. It is likewise known to attack the growth of algae by means of copper ions and to make water germ free by means of silver salts. Descriptions are found also of a combination of peroxide compositions and silver or copper ions as well as the combination of quaternary ammonium compositions and hydrogen peroxide (c.f. DE-A-2 235 539, DE-A-2 530 487 and DE-A-2 911 288).
DE-A-2 600 466 and DE-A-3 423 703 describe methods of preventing the growth of algae in aqueous systems wherein the algae are contacted with a condensation product of tetramethylethylenediaminedihydrochloride and epichlorohydrine. DE-A-3 247 536 discloses algicide condensates of diamino alkanes and urea or epichlorohydrine. However, it was found that these condensates are not satisfactory in their algicide effect so that usually they are applied in combination with heavy metal ions in order to achieve sufficient effectiveness.
Algicide mixtures based on monomer quaternary ammonium compositions and copper salts are disclosed in U.S. Pat. No. 4,098,602. The ammonium compositions used in that case are salts of the benzalkonium type. These compositions, however, lead to the undesired formation of foam and have the further disadvantage of developing a disturbing odor.
EP-A-59 978 describes a process for the removal of algae wherein a quaternary ammonium composition is used in combination with water soluble copper salts and/or silver salts and a peroxide composition setting free oxygen. Suitable quaternary ammonium compositions are poly(diallyldimethylammoniumchloride), poly(1,4-bis(dimethylazonia)-7-oxanonylenedichloride) and poly(1,4-bis(dimethylazonia)-6-hydroxyheptylenedichloride).
The use of a condensation product of tetramethylhexamethylenediamine and 1,3-di-bromopropane is described as a bactericide, especially in combination with copper and silver ions, in WO 87/02221. An algicide effect of this condensate is not mentioned.
GB-A-2 194 227 discloses the use of a polymeric cationic quaternary ammonium composition together with a copper salt, a gelating agent, and an oxidizing agent for the treatment of water, especially in swimming pools.
Yet it was found that the quaternary ammonium compositions of the benzalkonium type used to remove algae from water tend to form foam and, what is more, have an unpleasant odor. The polymeric quaternary ammonium compositions, on the other hand, have an insufficient algicide effect and, therefore, as a rule, must be used in combination with metal ions, such as copper, silver, or manganese ions. The addition of such metal ions, however, is undesired for various reasons. For instance, the addition of copper and silver ions leads to increased corrosion of the metal tubes present in the water system under treatment because of the series of electrochemical potentials. Under the influence of reducing agents and with the effect of light silver ions provide black silver deposits. Furthermore, the use of heavy metal ions is undesirable for reasons of price and for reasons of environmental protection.
EP-A-0 203 892 finally describes the use of polymeric ammonium compositions to fight noxious organisms in water systems, the dimethylammonium groups of these compositions being separated alternatingly by alkylene groups and dibenzyl groups. DE-A-24 38 035 describes biocide mixtures which consist of chemical complexes or mixtures of a quaternary ammonium composition and an isothiazolin-3-on-composition.